1. Field
This disclosure relates generally to a receiver in a communications system, and more specifically to a receiver adapted to switch between a plurality of modes in response to monitored metrics within the receiver.
2. Related Art
Receivers in communication systems used to receive radio frequency signals can use many ways to demodulate a selected signal to recover a baseband signal or data. For example, some receivers use a superheterodyne architecture or scheme to remove a carrier frequency from a received signal to produce a baseband signal. Such a superheterodyne architecture can use one or more frequency shifts (e.g. heterodyning processes) to produce one or more intermediate signals with successively lower intermediate frequencies until finally producing a baseband signal. In one architecture, a receiver can use a very low intermediate frequency (VLIF) where a received signal is shifted down to a very low intermediate frequency, which can be subsequently down converted to a baseband signal. In yet another type of receiver, the received frequency can be down converted to baseband in a single mixing operation. This type of receiver is known as a zero intermediate frequency (ZIF) receiver or a direct conversion receiver.
By using a low IF architecture, the advantages of a superheterodyne structure can be combined with the advantages of direct conversion architecture. For example, IF selectivity can be realized using low frequency analog and digital filtering. In the VLIF architecture, the fact that the local oscillator signal is not the same frequency as the desired, or on-channel signal, minimizes DC offset and 1/f noise problems inherent in the direct conversion architecture. However, mixer imbalance issues can limit image rejection in a VLIF receiver, which can reduce the adjacent channel rejection performance of the VLIF receiver. To compensate for poor adjacent channel rejection performance, some VLIF receivers may use costly calibration circuits and procedures.